UPDATED TO 1.21.4!!

A while ago, I added vertical half-slabs to Minecraft because no one had done it in a way that I liked. It wasn't great, but now it uses Display Entities instead of Item Frames, and uses a LOT fewer commands.

To get a vertical half-slab, just sneak while holding a slab (copper slabs must be waxed first).
The pack will detect when you are bridging with slabs and not place vertical slabs.

IMPORTANT NOTE:
Upgrading worlds using old versions of this datapack is not supported. There is no way to automatically upgrade.

This pack is FINALLY compatible with other packs which alter the Item Frame Item Model. Because this doesn't use that model at all.
As of 1.21.4 this is the nicest iteration of this pack.